Did your son earn more than $12,550 in 2021? Your son does not owe taxes or have to file a return unless he earned more than $12,550 during 2021. That's assuming your teenage son is living with you and is listed as a dependent on your annual tax filing.
Did your son receive a 1099? Were taxes deducted from your's son's payments? Even though your son might not have any income tax liability, two situations may warrant a separate tax filing: (1) in the unlikely event he receives a W-2 form (he was an employee) and taxes were deducted from his payments, he would need to file in order to get a refund; and (2) if he received more than $400 as a self-employed musician (for example, he received a Form 1099 indicating a $500 payment), he would need to pay self-employment tax. Note, the $400 figure is determined after deducting your son's expenses from his total income. So, for example, if he received a Form 1099 indicating a $500 payment but he had $200 in studio expenses, your son would not reach the $400 threshold.